The present invention relates generally to a sole structure for a shoe, and more particularly, to an improved sole structure for improving cushioning properties, causing a smooth ride feeling, and improving a lateral stability during walking or running.
We proposed a sole structure such as shown in WO 2006/129837. The sole structure is comprised of an upper plate, a wavy corrugated lower plate disposed under the upper plate and having two bulges to form a void with the upper plate, and an elastic block to couple an upwardly convex portion formed between the adjacent bulges to the upper plate.
Also, Japanese patent application laying-open publication No. 9-248203 (JP 9-248203) shows a midsole structure comprised of a dispersion portion formed of synthetic resin and disposed on the upper side of the structure, a ground contact portion disposed on the lower side of the structure, and a buffer portion formed of a plurality of longitudinally continuous V-shaped portions and disposed between the dispersion portion and the ground contact portion. An upper end of each of the V-shaped portions extends to a side edge portion of the dispersion portion.
In the above-mentioned sole structure shown in WO 2006/129837, at the time of a shoe strike onto the ground, each of the bulges of the lower plate compressively deforms into a more flattened shape and the void between the upper and lower plates thus functions as a cushioning hole to absorb an impact load.
Also, in this case, the elastic block shearing-deforms in the longitudinal direction during walking or running and the upper plate thus sways to and fro. Thereby, a smooth ride feeling can be achieved.
However, in the sole structure like this, when the shoe impacts the ground, the elastic block is so constructed as to shearing-deforms not only in the longitudinal direction but also in the lateral direction. As a result of this, depending on the rigidity of the elastic block, the upper plate may sway in the lateral direction at the time of the shoe strike onto the ground.
On the other hand, the above-mentioned JP 9-248203 describes that an impact load applied to the ground contact portion at the time of the shoe strike onto the ground is dispersed at each of the V-shaped portions of the buffer portion and transmitted to the dispersion portion and the cushioning properties thus improves.
Also, in this case, since the upper end of each of the V-shaped portions extends to the side edge portion of the dispersion portion, it may be possible that a lateral sway at the time of the shoe strike onto the ground is prevented in some degree.
However, in the midsole structure like this, each of the V-shaped portions is structured such that it is hard to be shearing-deformed in the longitudinal direction because the buffer portion is formed of a plurality of longitudinally continuous V-shaped portions and the upper end of each of the V-shaped portions is fixed to the dispersion portion. Thereby, the dispersion portion disposed on the upper side cannot sway to and fro during walking or running and as a result a smooth ride feeling cannot be achieved.
The present invention is directed to providing a sole structure for a shoe that can improve cushioning properties, that can provide a smooth ride feeling, and that can improve stability in the lateral direction.
Other objects and advantages of the present invention will be obvious and appear hereinafter.